PowerShell: Fix handling of subexpressions nested inside of double quoted strings

[thecityofguanyu]

This MR will:

• Add a new "unless" condition to an existing "push :paramters" declaration in a rule in the :root state to fix handling of subexpressions nested in strings.
• Fix side effect of that change by adding a new rule for detection of "2>" style output redirection.

Intended to address issue #1757. That issue links to a sample of the bug on rouge.jneen.net.

I was stepping through the debugger when invoking rougify against a local PowerShell file that contains a subexr nested in a string. I'm debugging using Rouge 3.26.1, Ruby 2.6.8p205.

Below is the relevant snippet that of my PowerShell file that the bug surfaces on:

function NewVMSnapshot {
    param(
        [Parameter(Mandatory = $true)]
        [string[]]$VM,
        [string[]]$Name = (Get-Date -Format 'yyyy-MM-dd_HH:mm:ss') + "_$VM",
        [string[]]$Description = "`Snapshot taken via $(Split-Path $PSCommandPath -leaf) by $global:vsphereuser."
    )

    try {

Once it reached the by part of the string in the [string[]]$Description line, the debugger ends up hitting this rule that's defined in the :root state:

        rule %r/([\/\\~[a-z]][-.:\/\\~\w]*)(\n)?/i do |m|
          groups Name, Text::Whitespace
          push :parameters
        end

I'm not sure why it's hitting that, but it results in :parameters being pushed to the stack. And since :parameters is pushed to the stack, once it finally hits that closing double quote, it just treats it as a new double quote and pushes another :dq onto the stack -- which is on top of the old one.

Screenshot of the stack below.

I'm a complete Ruby novice here therefore also a Rogue novice, so my justification for the changes may be tenuous. Feel free to poke holes in it and suggest more appropriate fixes should they be obvious.